Offshore platforms for various uses, including ocean research, are in widespread use throughout the world. The majority of these platforms are found in the offshore petroleum industry in exploration and production functions.
The offshore drilling industry and technology associated with it have developed rapidly in the last 30 years. The drilling rigs in use today have evolved into sophisticated structures, designed and built to withstand the severest of environmental conditions and to operate in very deep waters. Advanced computer technology has contributed substantially to bring platform development to its present position. Computers are integral, for example, to the collection and evaluation of geological and seismic data, to the operation of dynamically positioned platforms, and to methods of well control.
Furthermore, such modern technology has led to the development of platforms serving various functions and which are in the normal course of operation unmanned. Characteristically, these unmanned platforms are required to be maintained on a regular basis and to therefore be accessible to maintenance crews. Currently and for some years access to these platforms has been by helicopter. There are, however, very significant disadvantages in the use of helicopters to access platforms. The platform structure itself is required to be provided with a helicopter landing pad. This is a very significant expense and, as well, an engineering disadvantage on many small platforms. Finally, helicopter usage is the single most dangerous aspect of the offshore industry.
These normally unmanned platforms are required to carry lifeboats and launch systems for use in case a life threatening situation develops while a maintenance crew is on the platform.
As is well documented, evacuation systems used in emergency evacuation of offshore platforms have not performed well with resulting high loss of life. There has therefore been an ongoing search for more reliable evacuation systems.
At the same time, the increasing use of unmanned platforms, and the problems discussed above incident to those platforms, have led to a need for better access systems for such platforms.
The applicant herein has developed several access and evacuation systems to address a number of the problems discussed above, including the development of a unique marine access craft for use in the systems. Reference may be had, for example, to applicant's U.S. Pat. No. 5,341,761, "Evacuation System", U.S. Pat. No. 4,781,144, "Off-Shore Drilling Installation Evacuation System" and U.S. Pat. No. 5,706,755, "Access and Evacuation System for Offshore Platform".
In some instances, however, certain geographic locations dictate specific design needs to the access and evacuation system. For example, the prevailing tides or water conditions may require a different launching mechanism for the evacuation craft, or an ice buildup around the offshore platform may require that the craft be placed in the water in a different manner than current systems. One such example is the "100 year ice rubble condition" found north of Sakhalin Island in the Sea of Okhotsk in eastern Russia, in which the ice rubble can be expected to extend out approximately 25 meters beyond the edge of the platform. There are no existing systems which are specifically designed to address this severe ice rubble problem.
Against this background, the present invention combines aspects of applicant's previous systems with a unique articulated deployment arm to address a number of the problems discussed above. A unique support bracket and deployment mechanism for the marine access craft is provided for use in the system.
A number of systems have described the use of an articulated or segmented arm for evacuation of personnel from ships or floating platforms and for the loading and unloading of cargo or smaller vessels to and from ships.
U.S. Pat. No. 3,596,623 of Frankel, issued Aug. 3, 1971, describes an apparatus for coupling a smaller ship to a larger ship. The apparatus taught in that reference relies upon buoyancy means to "float" the second portion of the coupling platform to a location in the water to receive the small ship.
U.S. Pat. No. 4,202,427 of Sada, issued May 13, 1980, describes a complicated structure in which an A-frame is releasably secured to a platform. The A-frame is released and is moved to a secondary position controlled by guy wires, at the same time as the hangar spar rotates away from the A-frame into a vertical position, after which the wires control the lowering of the personnel capsule vertically onto an escape vessel, such as a ship, or onto another level of the platform.
U.S. Pat. No. 4,633,802 of Olsen, issued Jan. 6, 1987, provides an apparatus for launching a float or the like from a ship in which an upper portion of the arm is fixed in position relative to the ship. The lower portion is releasably secured to the upper portion and upon release, is biased into a launch position by a spring connecting the upper and lower portions, in a catapult like fashion. The float is then launched into the water. The device is not suitable for evacuating personnel but is designed for placing floats, buoys and the like in the water.
U.S. Pat. No. 5,253,606 of Ortelli, issued Oct. 19, 1993, provides a machine for gripping, securing and handling underwater vehicles and the like in which the portions of an articulated arm are controlled by a piston on each portion. The lower portion is permitted to move in several directions to assist alignment with the object to be gripped.